Cisco Press
201 West 103rd Street
Indianapolis, IN 46290 USA

Cisco Press
CCNA Self-Study

CCNA INTRO
Exam Certification Guide

Wendell Odom, CCIE No. 1624

0945_01f.book Page i Wednesday, July 2, 2003 3:53 PM

ii

CCNA INTRO Exam Certification Guide

Wendell Odom
Copyright© 2004 Cisco Systems, Inc.
Published by:
Cisco Press
201 West 103rd Street
Indianapolis, IN 46290 USA
All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permis-
sion from the publisher, except for the inclusion of brief quotations in a review.
Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
First Printing August 2003



0945_01f.book Page ii Wednesday, July 2, 2003 3:53 PM

iii

Publisher:

John Wait

Cisco Representative:

Anthony Wolfenden

Editor-In-Chief:

John Kane

Cisco Press Program Manager:

Sonia Torres Chavez

Executive Editor:

Brett Bartow

Cisco Marketing Communications Manager:

Scott Miller

Managing Editor:


Cover Designer:

Louisa Adair

Compositor:

Mark Shirar

Indexer:

Tim Wright

0945_01f.book Page iii Wednesday, July 2, 2003 3:53 PM

iv

About the Author

Wendell Odom, CCIE No. 1624,

is a senior instructor with Skyline Computer
(www.skylinecomputer.com), where he currently teaches courses on QoS, CCNA, and CCIE
lab preparation. Wendell has worked in the networking arena for 20 years, with jobs in pre-
and post-sales technical consulting, teaching, and course development. He has authored
portions of more than 12 courses, including topics such as IP routing, MPLS, Cisco WAN
switches, SNA protocols, and LAN troubleshooting. He is author of three previous editions
of the

CCNA Exam Certification Guide

. He holds a bachelor’s degree in
international business from Westminster College. Martin Walshaw

, CCIE No. 5629, CISSP, CCNP, CCDP, is a systems engineer working for
Cisco Systems in the Enterprise Line of Business in South Africa. His areas of specialty
include convergence, security, and content delivery networking, which keeps him busy both
night and day. During the last 15 years or so, Martin has dabbled in many aspects of the IT
industry, ranging from programming in RPG III and COBOL to PC sales. When Martin is
not working, he likes to spend all of his available time with his patient wife, Val, and his sons,
Joshua and Callum. Without their patience, understanding, and support, projects such as this
would not be possible.

0945_01f.book Page iv Wednesday, July 2, 2003 3:53 PM

v

Dedications

Chris Cleveland is the best Development Editor I could imagine working with. So, instead of
just the usual “Thanks Chris for doing an excellent job,” I’d like to dedicate this book to
Chris. Chris, it’s an absolute pleasure to work with the best in the business —thanks for your
fantastic help and support!

Acknowledgments

The technical editing team for this book and its companion volume was fantastic! Not only did they
find where I had simply written the wrong technical facts, but they also helped me find new, more

the least pain for the author, Chris is on top of it. Thanks, Chris, for all you do!

0945_01f.book Page v Wednesday, July 2, 2003 3:53 PM

vi

Contents at a Glance

Introduction xvii

PART I: Networking Fundamentals 3

Chapter 1 Introduction to Computer Networking Concepts 5
Chapter 2 The TCP/IP and OSI Networking Models 15
Chapter 3 Data Link Layer Fundamentals: Ethernet LANs 43
Chapter 4 Fundamentals of WANs 77
Chapter 5 Fundamentals of IP 109
Chapter 6 Fundamentals of TCP and UDP 145

PART II: Operating Cisco Devices 169

Chapter 7 Operating Cisco Routers 171
Chapter 8 Operating Cisco LAN Switches 209

PART III: LAN Switching 227

Chapter 9 Cisco LAN Switching Basics 229
Chapter 10 Virtual LANs and Trunking 259
Chapter 11 LAN Cabling, Standards, and Topologies 279


Part I Networking Fundamentals 3

Chapter 1 Introduction to Computer Networking Concepts 5

Perspectives on Networking 5

The Flintstones Network: The First Computer Network? 7

Chapter 2 The TCP/IP and OSI Networking Models 15

“Do I Know This Already?” Quiz 16
Foundation Topics 20
The TCP/IP Protocol Architecture 21

The TCP/IP Application Layer 22
The TCP/IP Transport Layer 24
The TCP/IP Internetwork Layer 26
The TCP/IP Network Interface Layer 27
Data Encapsulation 29

OSI Reference Model 31

OSI Layers 31
OSI Layering Concepts and Benefits 34
OSI Terminology 35
OSI Summary 37

Foundation Summary 38
Q&A 41


0945_01f.book Page vii Wednesday, July 2, 2003 3:53 PM

viii

Ethernet Data-Link Protocols 63

Ethernet Addressing 64
Ethernet Framing 65
Identifying the Data Inside an Ethernet Frame 66
Layer 2 Ethernet Summary 68

Recent Ethernet Standards 68

Fast Ethernet 68
Gigabit Ethernet 69

Foundation Summary 70
Q&A 74

Chapter 4 Fundamentals of WANs 77

“Do I Know This Already?” Quiz 77
Foundation Topics 81
OSI Layer 1 for Point-to-Point WANs 81

WAN Connections from the Customer Viewpoint 84

WAN Cabling Standards 85
Clock Rates, DCE, and DTE 88
Link Speeds Offered by Telcos 89

Routing (Path Selection) 114

PC1’s Logic: Sending Data to a Nearby Router 114
R1 and R2’s Logic: Routing Data Across the Network 115
R3’s Logic: Delivering Data to the End Destination 116

Network Layer Interaction with the Data Link Layer 116

0945_01f.book Page viii Wednesday, July 2, 2003 3:53 PM

ix

Network Layer (Layer 3) Addressing 118

Example Layer 3 Address Structures 119

Routing Protocols 119

IP Addressing Fundamentals 120

IP Addressing Definitions 120
How IP Addresses Are Grouped Together 121
Classes of Networks 122

The Actual Class A, B, and C Network Numbers 124
IP Subnetting 124
Network Layer Utilities 127

Address Resolution Protocol and the Domain Name System 127
ICMP Echo and the ping Command 130

Foundation Summary 164
Q&A 167

Part II Operating Cisco Devices 169

Chapter 7 Operating Cisco Routers 171

“Do I Know This Already?” Quiz 171
Foundation Topics 176
The Cisco IOS Software Command-Line Interface 176

Access to the CLI 176
CLI Help Features 179
The

debug

and

show

Commands 181

0945_01f.book Page ix Wednesday, July 2, 2003 3:53 PM

x

Configuring Cisco IOS Software 181

Example Configuration Process 183

Configuring 2950 IOS Software 220
Foundation Summary 221
Q&A 223

Part III LAN Switching 227

Chapter 9 Cisco LAN Switching Basics 229

“Do I Know This Already?” Quiz 229
Foundation Topics 234
The Case for Bridging and Switching 234
Transparent Bridging 236

The Forward Versus Filter Decision 237
How Bridges Learn MAC Addresses 239
Forwarding Unknown Unicasts and Broadcasts 240

LAN Switching 240

Full-Duplex Ethernet 242
Internal Processing on Cisco Switches 242
Speed and Autonegotiation 244
Summary: Bridges and Switches 244

LAN Segmentation 245
The Need for Spanning Tree 248

How Spanning Tree Works 249

Foundation Summary 252

Foundation Summary 274
Q&A 276

Chapter 11 LAN Cabling, Standards, and Topologies 279

“Do I Know This Already?” Quiz 279
Foundation Topics 283
Network Topologies 283
Cabling and Connectors 287

General Features of Metallic Cabling 287
Unshielded Twisted-Pair and Shielded Twisted-Pair Cabling and Connectors 289

UTP Standards 290
UTP Connectors 290

Coaxial Cabling 291
Fiber-Optic Cabling and Connectors for Ethernet 293

Optical Connectors for Ethernet 295

Summary: Ethernet Cabling 297

Ethernet Standards 297

Ethernet Framing 298
Ethernet Cabling Standards 298
10-Gigabit Ethernet 299

Wireless Communications 300


Finding the Subnet Number 333
Finding the Subnet Broadcast Address 335
Finding the Range of Valid IP Addresses in a Subnet 336
Finding the Answers Without Using Binary 338

What Subnet Masks Meet the Stated Design Requirements? 344
What Are the Other Subnet Numbers? 347

Scaling the IP Address Space for the Internet 351

CIDR 351
Private Addressing 353
Network Address Translation 354
IP Version 6 Addressing 355

Foundation Summary 356
Q&A 358

Chapter 13 Basic Router Configuration and Operation 363

“Do I Know This Already?” Quiz 363
Foundation Topics 368
Configuring IP Addresses 368

Basic Administrative Configuration 370
Configuring IP Addresses 372

Prefix Notation 375
Seeding the Routing Table with Connected IP Routes 375

Balanced Hybrid Protocols: Enhanced IGRP 419
Summary of Interior Routing Protocols 420
Foundation Summary 422
Q&A 425
Part V Wide-Area Networking 427
Chapter 15 Remote Access Technologies 429
“Do I Know This Already?” Quiz 429
Foundation Topics 435
Perspectives on the PSTN 435
Converting Analog Voice to Digital Voice 438
Analog Modems 441
Modulation and Demodulation 442
Point-to-Point Protocol Features with Modems 444
Modem Installation and Cabling 445
Modem Standards 446
Analog Modem Summary 447
Integrated Services Digital Network 447
ISDN Channels 449
ISDN Call Setup and Data Link Protocols 449
Typical Uses of ISDN 451
ISDN Installation and Cabling 453
ISDN Summary 453
Digital Subscriber Line 454
DSL Standards 456
DSL Protocols 458
DSL Summary 459
Cable Modems 460
Layer 1 and Layer 2 between the Home and the Head End 462
Upstream Data 463
Cable Modem Summary 464

Switch
ATM
Switch
ISDN/Frame Relay
Switch
Communication
Server
Gateway
Access
Server
PC PC with
Software
Sun
Workstation
Macintosh
Terminal File
Server
Web
Server
Cisco Works
Workstation
Printer Laptop IBM
Mainframe
Front End
Processor
Cluster
Controller
Modem
0945_01f.book Page xv Wednesday, July 2, 2003 3:53 PM
xvi

Congratulations! If you’re reading far enough to look at the introduction to this book, then
you’ve probably already decided to go for your Cisco Certified Network Associate (CCNA)
certification. Cisco System’s entry-level certification, CCNA, has a reputation as one of the
most valuable entry-level certifications in the computing industry. Although getting your
CCNA does not guarantee you a first networking job or a new job, it will certainly help
convince others that you know what you are talking about.
Cisco’s CCNA certification proves that you have a firm foundation in the most important
components of the Cisco product line—namely, routers and switches. It also proves that you
have a broad knowledge of protocols and networking technologies. CCNA is not an easy
certification to get, but it is well worth the effort. In a booming economy, CCNA is the first
step toward getting a higher salary than your noncertified peers. In a difficult economy, it
could be the difference between whether a prospective employer even looks at your résumé.
Regardless of your local economy, CCNA does improve how people in the marketplace view
your skill level.
People ask me for career advice from time to time, and my answer is typically the same: If
you want to be in the networking industry at all, you need to know Cisco. Cisco has some
ridiculous market shares in the router and switch marketplace, with more than 80% market
share in some markets. In many geographies and many markets, networking equals Cisco. If
you want to be taken seriously as a network engineer, you need a CCNA certification.
Frankly, you probably also need to be working toward a more advanced Cisco certification
as well—but first things first! CCNA requires some time and effort.
Cisco’s Motivation: Certifying Partners
Cisco’s primary motivation for creating CCNA and most of the other Cisco certifications is
to help determine the skill levels of its partners. Cisco fulfills only a small portion of its orders
through direct sale from Cisco; most often, a Cisco reseller is involved. (Cisco calls resellers
channel partners.) Also, Cisco encourages partners to perform most consulting and
implementation services relating to Cisco products. While working heavily with partners,
Cisco needed to know which partners truly had the right skills. So, Cisco created many
certifications, including CCNA.
Cisco measures the technical readiness of channel partners (resellers) and professional

on to the ICND exam.
Table I-1
CCNA Exam Names and Numbers
Exam Name
Exam
Number Comment
Introduction to Cisco Networking
Technologies (INTRO) exam
640-821 A subset of the CCNA topics; should be
taken before the ICND exam
Interconnecting Cisco Network
Devices (ICND) Exam
640-811 A subset of the CCNA topics; should be
taken after the INTRO exam
CCNA Exam 640-801 Can be taken instead of INTRO and
ICND exams; covers the same content
as the other two exams combined
0945_01f.book Page xviii Wednesday, July 2, 2003 3:53 PM
xix
Format of the CCNA Exams
The INTRO, ICND, and CCNA exams all follow the same general format. When you get to
the testing center and check in, the proctor will give you some general instructions and then
take you into a quiet room with a PC. When you’re at the PC, you have a few things to do
before the timer starts on your exam—for instance, you can take a sample quiz, just to get
accustomed to the PC and to the testing engine. Anyone who has user-level skills in getting
around a PC will have no problems with the testing envinronment.
When you start the exam, you will be asked a series of questions. You answer the question
and then move on to the next question. The exam engine does not let you go back and change
your answer. Yes, that’s true—when you move on to the next question, that’s it for the earlier
question.

Netsim product, compiled specifically for this book, is also included on the CD that comes
with this book.
What’s on the CCNA Exam(s)?
Ever since I was in grade school, whenever the teacher announced that we were having a test
soon, someone would always ask, “What’s on the test?” Even in college, people would try to
get more infomrmation about what would be on the exams. At heart, the goal is to know
what to study hard, what to study a little, and what to not study at all.
Cisco does want you to know what topics to study and wants you to be well prepared for
your exams. However, Cisco does not want to be so specific that you could just memorize a
certain set of facts and pass the exams. In short, Cisco wants you to pass the exams because
you know your stuff, not because you memorized a set of questions that someone posted
(possibly illegally) on an Internet site.
So, what can be said about the content of the exams? First, Cisco posts exam topics for each
exam. This official posting is the basis for what Cisco intends to put on the exams, so you
should pay particularly close attention to this list. Also, the breadth and depth of topics on
the exams tend to match the Cisco Authorized courses with which they are associated, so it
is useful to know the outlines for those courses. Finally, Cisco designs the Cisco Networking
Academy Program (CNAP) course materials with CCNA in mind. Looking at all these
sources can help give you insight into CCNA.
INTRO Exam Topics
Carefully consider the exam topics posted by Cisco on its web site as you study, particularly
for clues as to how deeply you should know each topic. The exam topics use action words
that follow a quasi-standard called Bloom’s Taxonomy of the Cognitive Domain. Bloom’s
taxonomy defines a standard for word usage for when educators create objectives for
courses. Objectives written according to Bloom’s taxonomy define what the learner (student)
should be able to accomplish after taking the class. So, when you look at an exam topic, look
for the action word. If you want to see a description of Bloom’s taxonomy, search the
Internet, and you will find a lot of matches. My favorite quick list of terms is at

The action word in the exam topic gives you a good hint about the level of knowledge and

Design & Support
1 Use a subset of Cisco IOS commands to analyse and report network
problems
2 Use embedded layer 3 through layer 7 protocols to establish, test,
suspend or disconnect connectivity to remote devices from the router
console
3 Determine IP addresses
Implementation & Operation
4 Establish communication between a terminal device and the router
IOS, and use IOS for system analysis
5 Manipulate system image and device configuration files
continues
0945_01f.book Page xxi Wednesday, July 2, 2003 3:53 PM
xxii
Exam Topic
Reference Number Exam Topic
6 Perform an initial configuration on a router and save the resultant
configuration file
7 Use commands incorporated within IOS to analyse and report
network problems
8 Assign IP addresses
9 Describe and install the hardware and software required to be able to
communicate via a network
10 Use embedded data link layer functionality to perform network
neighbor discovery and analysis from the router console
11 Use embedded layer 3 through layer 7 protocols to establish, test,
suspend or disconnect connectivity to remote devices from the router
console
Technology
12 Demonstrate the mathematical skills required to work seamlessly

24 Describe how an IP address is associated with a device interface, and
the association between physical and logical addressing
25 Employ IP addressing techniques
26 Compare and contrast collision and broadcast domains, and describe
the process of network segmentation
27 Describe the principles and practice of switching in an Ethernet
network
28 Explain how collisions are detected and handled in an Ethernet
system
29 Explain the fundamental concepts associated with the Ethernet media
access technique
30 Describe how the protocols associated with TCP/IP allow host
communication to occur
31 Describe the operation of the Internet Control Message Protocol
(ICMP) and identify the reasons, types and format of associated error
and control messages
32 Describe the principles and practice of packet switching utilizing the
Internet Protocol (IP)
33 Describe, compare and contrast network communications using two
examples of layered models (OSI and IETF)
34 Describe the fundamental concepts associated with transport layer
protocols, and compare the connectionless approach to transport
with the connection oriented one
35 List the major TCP/IP application protocols, and briefly define their
features and operation
36 Describe the operation of the major transport layer protocols TCP
and UDP and the interaction and carriage of application layer data
37 Perform an initial configuration on a switch and save the resultant
configuration file
Table I-2

13 1 – 5 31 4
14 1 - 5 32 1, 4
15 1 33 1
16 1, 3 34 1
17 1, 5 35 1
18 2 36 1
37 2
0945_01f.book Page xxiv Wednesday, July 2, 2003 3:53 PM
xxv
every possible fact. So, you should expect the CCNA exam to include questions that cover
more advanced topics, many of which require that you know the more basic facts. For
instance, rather than ask a question about how to do binary math, which is specifically
mentioned for the INTRO exam topics, you might have to derive subnet numbers – which
requires you to use binary math. Another example: instead of describing LAN cabling, you
might have a question about troubleshooting a LAN topology, and need to decide if an
incorrect type of cable was used. So, while the exam topics do not exactly match up, but you
essentially need to know all the same concepts on both the INTRO and ICND exams in order
to succeed on the CCNA exam.
Table I-4 lists the CCNA exam topics at time of publication. As always, look to
www.cisco.com for the latest posted information about the CCNA, INTRO, and ICND
exams!
Table I-4
CCNA Exam Topics
Exam Topic
Reference Number Exam Topic
Planning and Design
1 Design a simple LAN using Cisco Technology
2 Design an IP addressing scheme to meet design requirements
3 Select an appropriate routing protocol based on user requirements
4 Design a simple internetwork using Cisco technology